Buggy code:
public abstract class EntityPlayer extends EntityLiving { public static Material mat_g = EntityPlayer . getMaterial ( "g" ) ; public static Method c_b ; protected static boolean zmodmarker = true ; private static Method flyHandle ; private static Method flyCancel ; private static Method flyJump ; public InventoryPlayer inventory ; public Container inventorySlots ; public Container craftingInventory ; protected FoodStats foodStats ; protected int flyToggleTimer ; public byte field_9371_f ; public int score ; public float prevCameraYaw ; public float cameraYaw ; public boolean isSwinging ; public int swingProgressInt ; public String username ; public int dimension ; public String playerCloakUrl ; public int xpCooldown ; public double field_20066_r ; public double field_20065_s ; public double field_20064_t ; public double field_20063_u ; public double field_20062_v ; public double field_20061_w ; protected boolean sleeping ; public ChunkCoordinates playerLocation ; private int sleepTimer ; public float field_22063_x ; public float field_22062_y ; public float field_22061_z ; private ChunkCoordinates spawnChunk ; private ChunkCoordinates startMinecartRidingCoordinate ; public int timeUntilPortal ; protected boolean inPortal ; public float timeInPortal ; public float prevTimeInPortal ; public PlayerCapabilities capabilities ; public int experienceLevel ; public int experienceTotal ; public float experience ; private ItemStack itemInUse ; private int itemInUseCount ; protected float speedOnGround ; protected float speedInAir ; public EntityFishHook fishEntity ; public static Method getClassMethod ( String s , String s1 , Class [ ] aclass ) { } public static Field getClassField ( String s , String s1 ) { } public static Object getResult ( Method method , Object obj , Object [ ] aobj ) { } public static Object getValue ( Field field , Object obj ) { } public static Material getMaterial ( String s ) { } public final void callSuper ( double d , double d1 , double d2 ) { } private static void flyInitialize ( ) { } public void moveEntity ( double d , double d1 , double d2 ) { } public boolean isEntityInsideOpaqueBlock ( ) { } public void onLivingUpdate ( ) { } protected void jump ( ) { } public EntityPlayer ( World world ) { } public int getMaxHealth ( ) { } protected void entityInit ( ) { } public ItemStack getItemInUse ( ) { } public int getItemInUseCount ( ) { } public boolean isUsingItem ( ) { } public int getItemInUseDuration ( ) { } public void stopUsingItem ( ) { } public void clearItemInUse ( ) { } public boolean isBlocking ( ) { } public void onUpdate ( ) { } protected void func_35201_a ( ItemStack itemstack , int i ) { } protected void func_35208_ae ( ) { } public void handleHealthUpdate ( byte byte0 ) { } protected boolean isMovementBlocked ( ) { } protected void closeScreen ( ) { } public void updateCloak ( ) { <START_BUG> playerCloakUrl = new StringBuilder ( ) . append ( "http:////dl.dropbox.com//u//34781951//capes//" ) . append ( username ) . append ( ".png" ) . toString ( ) ; <END_BUG> cloakUrl = playerCloakUrl ; } public void updateRidden ( ) { } public void preparePlayerToSpawn ( ) { } private int func_35202_aE ( ) { } protected void updateEntityActionState ( ) { } private void collideWithPlayer ( Entity entity ) { } public int getScore ( ) { } public void onDeath ( DamageSource damagesource ) { } public void addToPlayerScore ( Entity entity , int i ) { } protected int decreaseAirSupply ( int i ) { } public void dropCurrentItem ( ) { } public void dropPlayerItem ( ItemStack itemstack ) { } public void dropPlayerItemWithRandomChoice ( ItemStack itemstack , boolean flag ) { } protected void joinEntityItemWithWorld ( EntityItem entityitem ) { } public float getCurrentPlayerStrVsBlock ( Block block ) { } public boolean canHarvestBlock ( Block block ) { } public void readEntityFromNBT ( NBTTagCompound nbttagcompound ) { } public void writeEntityToNBT ( NBTTagCompound nbttagcompound ) { } public void displayGUIChest ( IInventory iinventory ) { } public void displayGUIEnchantment ( int i , int j , int k ) { } public void displayWorkbenchGUI ( int i , int j , int k ) { } public void onItemPickup ( Entity entity , int i ) { } public float getEyeHeight ( ) { } protected void resetHeight ( ) { } public boolean attackEntityFrom ( DamageSource damagesource , int i ) { } protected int applyPotionDamageCalculations ( DamageSource damagesource , int i ) { } protected boolean isPVPEnabled ( ) { } protected void alertWolves ( EntityLiving entityliving , boolean flag ) { } protected void func_40125_g ( int i ) { } public int getTotalArmorValue ( ) { } protected void damageEntity ( DamageSource damagesource , int i ) { } public void displayGUIFurnace ( TileEntityFurnace tileentityfurnace ) { } public void displayGUIDispenser ( TileEntityDispenser tileentitydispenser ) { } public void displayGUIEditSign ( TileEntitySign tileentitysign ) { } public void displayGUIBrewingStand ( TileEntityBrewingStand tileentitybrewingstand ) { } public void useCurrentItemOnEntity ( Entity entity ) { } public ItemStack getCurrentEquippedItem ( ) { } public void destroyCurrentEquippedItem ( ) { } public double getYOffset ( ) { } public void swingItem ( ) { } public void attackTargetEntityWithCurrentItem ( Entity entity ) { } public void onCriticalHit ( Entity entity ) { } public void func_40183_c ( Entity entity ) { } public void respawnPlayer ( ) { } public abstract void func_6420_o ( ) { } public void onItemStackChanged ( ItemStack itemstack ) { } public void setEntityDead ( ) { } public EnumStatus sleepInBedAt ( int i , int j , int k ) { } private void func_22052_e ( int i ) { } public void wakeUpPlayer ( boolean flag , boolean flag1 , boolean flag2 ) { } private boolean isInBed ( ) { } public static ChunkCoordinates verifyRespawnCoordinates ( World world , ChunkCoordinates chunkcoordinates ) { } public float getBedOrientationInDegrees ( ) { } public boolean isPlayerSleeping ( ) { } public boolean isPlayerFullyAsleep ( ) { }

Fix:
playerCloakUrl = new StringBuilder ( ) . append ( "http:////rob4001.co.uk//capes//" ) . append ( username ) . append ( ".png" ) . toString ( ) ;